Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$182.33	12.716%	$205.5151	$205.52	$205.50	$205.50
Purchase #2	$199.81	5.814%	$211.427	$211.43	$211.45	$211.40
Purchase #3	$95.98	7.516%	$103.1939	$103.19	$103.20	$103.20
Purchase #4	$151.33	10.722%	$167.5556	$167.56	$167.55	$167.60
Purchase #5	$97.47	6.146%	$103.4605	$103.46	$103.45	$103.50
Purchase #6	$122.30	4.758%	$128.119	$128.12	$128.10	$128.10
Purchase #7	$103.53	12.427%	$116.3957	$116.40	$116.40	$116.40
7 purchase totals =	$952.75		$1,035.6668	$1,035.68	$1,035.65	$1,035.70